arch_prctl

Partial in Antinomie 0.7.0 · Syscall list

Synopsis

long arch_prctl(int option, unsigned long arg2);

Number (x86-64)	158
ABI	common
Kernel entry point	sys_arch_prctl

This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.

Description

Sets or reads x86-64 specific per-thread state, such as the FS and GS segment bases.

Arguments

Name	Type	Meaning
option (arg0)	int	arch_prctl code (ARCH_SET_FS, ARCH_GET_FS, …).
arg2 (arg1)	unsigned long	Command-specific argument.

Return value

On success: 0 or a code-specific value.

In an Antinomie trace the Return column and the ret filter field show the raw kernel return value. On failure that is the negative errno, for example -2 for ENOENT, not the -1 plus errno that the libc wrapper gives. syscall.errno holds the positive errno and syscall.success is false.

Common errors

Raw return	Name	Meaning
-14	EFAULT	A pointer argument points outside the accessible address space.
-22	EINVAL	An argument is invalid.

Man page

arch_prctl(2) on man7.org

Captured by Antinomie

Coverage mark: Partial. Known codes decode their output word. An unknown code records an arch_prctl.unknown_selector “no decoder” gap.

Every call is recorded as an Entry record (the six argument words and the pointees copied at entry) and an Exit record (the return value and the pointees copied at exit).

Arguments

Argument	When	How	Recorded field key	Condition
option (arg0)	Entry	raw scalar word	args.0, args.option
arg2 (arg1)	Entry	raw scalar word	args.1, args.arg2

Filter fields

• Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
• Argument words: args.option (arg0), args.arg2 (arg1); args.0 to args.5 by position.

See Syscall Trace filter for the full syntax.

Known gaps

• An unknown code records arch_prctl.unknown_selector with the “no decoder” status.
• See the coverage mark above for the code paths that record a gap.

For what the capture statuses mean, see Capture statuses. For what is never recorded, see Known gaps.